Historical Lorentz Interpretation and SR

Is there anyone here who could help me understand the state of physicists understanding just prior to 1905 and Einstein's SR paper? I keep running into length contraction, considerations of simultaneity and its non-universal nature, Lorentz transformations, time dilation and other concepts that seem to have been in the literature in 1904 and were (taken together and viewed from a modern perspective) incredibly close to SR. I understand that Einstein placed the correct interpretation of these concepts of space and time that weren't understood then, and I understand that he derived them from simpler concepts - relativity and the constancy of the speed of light.

What I'm wondering about is whether Lorentz and others of that time had actually reached the correct mathematical description of what we call SR. If so, how did they interpret their mathematics? Was it just that they couldn't make the conceptual leap to relativity and spacetime that Einstein made from the equations they had concluded must apply? Or had they not yet reached the correct mathematics? Was it a problem with interpretation or math?

I have read various articles on this, but none seem to really address my questions from this perspective.

Is there anyone here who could help me understand the state of physicists understanding just prior to 1905 and Einstein's SR paper? I keep running into length contraction, considerations of simultaneity and its non-universal nature, Lorentz transformations, time dilation and other concepts that seem to have been in the literature in 1904 and were (taken together and viewed from a modern perspective) incredibly close to SR. I understand that Einstein placed the correct interpretation of these concepts of space and time that weren't understood then, and I understand that he derived them from simpler concepts - relativity and the constancy of the speed of light.

What I'm wondering about is whether Lorentz and others of that time had actually reached the correct mathematical description of what we call SR. If so, how did they interpret their mathematics? Was it just that they couldn't make the conceptual leap to relativity and spacetime that Einstein made from the equations they had concluded must apply? Or had they not yet reached the correct mathematics? Was it a problem with interpretation or math?

I have read various articles on this, but none seem to really address my questions from this perspective.

Thanks for any guidance to someone who is merely curious.

The issue is interpretation but not that it was a problem. They just had a different way of looking at the issue. Actually, it was Einstein that had a different way of looking at the issue. Both ways of looking at the issue work, it's just that Einstein's way was simpler.

OK with that as background, scientists prior to Einstein believed in an absolute time that pervaded the entire universe. They understood that moving clocks would run slow but they were unwilling to interpret that as time running slow. They also assumed that the clocks were moving with respect to an absolute ether reference frame which they were unable to identify.

Einstein's insight was to assume that any reference frame could be treated identically to the so-called absolute ether frame if you just let time be redefined to be relative to that reference frame. This made for a simpler theory that was just as consistent in handling all the experimental evidence as the prior attempts that could never identify the frame in which time was absolute.

Is there anyone here who could help me understand the state of physicists understanding just prior to 1905 and Einstein's SR paper? I keep running into length contraction, considerations of simultaneity and its non-universal nature, Lorentz transformations, time dilation and other concepts that seem to have been in the literature in 1904 and were (taken together and viewed from a modern perspective) incredibly close to SR. I understand that Einstein placed the correct interpretation of these concepts of space and time that weren't understood then, and I understand that he derived them from simpler concepts - relativity and the constancy of the speed of light.

What I'm wondering about is whether Lorentz and others of that time had actually reached the correct mathematical description of what we call SR. If so, how did they interpret their mathematics? [..]

You already got several good leads; there wasn't much difference in opinion between them, it was mostly a difference in approach. SR as defined by Einstein was perhaps the first theory of physics without a metaphysical interpretation.

The issue is interpretation but not that it was a problem. They just had a different way of looking at the issue. Actually, it was Einstein that had a different way of looking at the issue. Both ways of looking at the issue work, it's just that Einstein's way was simpler.

This is a brief summary of my own understanding of how things stood. I understand that it took a real leap to give up absolute time/space, but I have two problems.

One is: If the mathematics give the same answers, I don't fully understand how one interprets the math other than with Einstein's interpretation. I wonder how the pre-Einstein physicist put it all together. I wonder if they just felt that the implications of the math just hadn't all been fully explored, or did they have what they believed was a consistent world view.

The second is: I have trouble giving Einstein the credit that others give him, at least for SR, if the math was the same. It makes me feel a bit guilty saying that - hindsight is so much easier. Certainly it was earth shattering to conclude that time actually did run slower, as compared to a clock that ran slower relative to some other absolute time, but I get this nagging impression that the same equations would eventually have driven physics to the SR viewpoint. I suspect Einstein was able to draw conclusions from his viewpoint/interpretation that went beyond what other physicists were able to draw, but if so, what were they?

OK with that as background, scientists prior to Einstein believed in an absolute time that pervaded the entire universe.

This part I understood.

They understood that moving clocks would run slow

I also understood this.

but they were unwilling to interpret that as time running slow.

And this, except that I couldn't understand how they reconciled the first part or interpreted the first part. Would the twin paradox have made any sense to them - even in the context of light waves/particles or other non-human clock aging where they understood that "clocks run slow"? Was it simply that they hadn't gone that far with the math they had in hand?

They also assumed that the clocks were moving with respect to an absolute ether reference frame which they were unable to identify.

I also understood this and that they had certain inconsistent experimental results.

Einstein's insight was to assume that any reference frame could be treated identically to the so-called absolute ether frame if you just let time be redefined to be relative to that reference frame. This made for a simpler theory that was just as consistent in handling all the experimental evidence as the prior attempts that could never identify the frame in which time was absolute.

I'm not denigrating this insight - it gave a "why" to the math and dragged everyone out of absolute time thinking into a new world of physics - but I wasn't sure if it was accurate to characterize the pre-Einstein math and the post-Einstein math as producing the same results with just a different spin put on it.

(Before the OP, I did read the wikipedia stuff on the history of SR, but thanks to those who posted it anyway.)

I think you have a very good understanding except that I would point out that there was nothing wrong with the concept of Absolute Time and an Absolute Ether as long as it is postulated. A consistent theory was developed. It's just that Einstein's second postulate was also consistent but simpler because it released scientists from being concerned about identifying the Absolute Ether. Technically speaking, if anyone wants to continue to promote an Ether Theory (such as LET), they should always use a single reference frame for everything and they should agree on which one it was but I think you can see why this would create unnecessary complexity and confusion.

You asked about the Twin Paradox. It's interesting to me that prior to Einstein, no one even considered the possibility of the Twin Paradox but Einstein predicted it in 1905 when he introduced Special Relativity. It shows his superior insight, in my opinion.

In my opinion, Einstein deserves all the credit for Special Relativity which is more than just the Principle of Relativity (his first postulate). It's his second postulate that makes all the difference and is not at all obvious that such a postulate could be proposed. Remember, the second postulate is not that the speed of light is constant, that was already a given under the first postulate, it was that light propagates at c in any inertial frame, which, as Einstein pointed out, seems to be at odds with the first postulate. He was able to see that it was not at odds and that insight may not have been discovered for a very long time if he had not paved the way for us.

[..] Would the twin paradox have made any sense to them - even in the context of light waves/particles or other non-human clock aging where they understood that "clocks run slow"? Was it simply that they hadn't gone that far with the math they had in hand?

It was only in 1904 that Lorentz's new theory was incepted, and it was only in the summer of 1905 that the "new mechanics" was perfected:
- https://en.wikisource.org/wiki/On_the_Dynamics_of_the_Electron_(June [Broken])

Thus I think that it is safe to say that indeed nobody had gone that far with the math at that time. Einstein gave a few months later the first clock retardation example, but still only from a single perspective (a paradox requires a minimum of two perspectives).

However, your question is indirectly answered by the oldest "twin perspective" example that I know of, by Langevin (from two perspectives, but still not "paradoxical"): see his article in 1911 which is a fascinating combination of ideas from Lorentz, Einstein and Minkowski. https://en.wikisource.org/wiki/The_Evolution_of_Space_and_Time
(The relevant "twin" discussion with Lorentz's interpretation starts from p.47).

[..] they should always use a single reference frame for everything and they should agree on which one it was but I think you can see why this would create unnecessary complexity and confusion.

Neither Newton nor Lorentz found any reason for introducing such complexity; evidently such things depend on how one reasons...

It's his second postulate that makes all the difference and is not at all obvious that such a postulate could be proposed. Remember, the second postulate is not that the speed of light is constant, that was already a given under the first postulate, it was that light propagates at c in any inertial frame [..]

You asked about the Twin Paradox. It's interesting to me that prior to Einstein, no one even considered the possibility of the Twin Paradox but Einstein predicted it in 1905 when he introduced Special Relativity. It shows his superior insight, in my opinion.

I completely agree. His insight is what makes SR so world shaking.

In my opinion, Einstein deserves all the credit for Special Relativity which is more than just the Principle of Relativity (his first postulate). It's his second postulate that makes all the difference and is not at all obvious that such a postulate could be proposed. Remember, the second postulate is not that the speed of light is constant, that was already a given under the first postulate, it was that light propagates at c in any inertial frame, which, as Einstein pointed out, seems to be at odds with the first postulate. He was able to see that it was not at odds and that insight may not have been discovered for a very long time if he had not paved the way for us.

So would the 1904 Lorentz have understood that two different observers, in two different IRFs moving at a constant speed relative to each other and looking at the same propagating light beam would each independently conclude that the light they were examining (with their co-moving instruments in their independent IRFs) was traveling at speed c relative to his IRF? Don't the LET equations force that?

I do understand that even with the correct equations in hand, the physical interpretation of those equations takes time and the radical reinterpretation of space and time resulting from SR was so great that Einstein deserves that credit. It's just that I want to understand what it is that I'm crediting him with. I want to see his work in the clearest possible light in the context of the time he did that work.

So would the 1904 Lorentz have understood that two different observers, in two different IRFs moving at a constant speed relative to each other and looking at the same propagating light beam would each independently conclude that the light they were examining (with their co-moving instruments in their independent IRFs) was traveling at speed c relative to his IRF? Don't the LET equations force that?

But that's the problem, you can't look at the propagation of a light beam. How would you do that? It's not like watching a bullet traveling at a high speed and which you shine light on so you can see where it is at any particular time. What do you use to watch the propagation of the light beam? I'm assuming of course that the beam has been just turned on and what you are talking about is the leading edge of the beam. Think about it.

This is the essence of the issue between scientists prior to Einstein and Einstein. They just assumed that light propagated at c only in the rest state of the ether that pervaded the universe. Einstein said that everything would work just fine if you made that exact same assumption in any inertial frame. But either way, there is no way to prove or measure or conclude in any absolute sense which assumption is correct. Einstein simply used the assumption as the basis for establishing what a frame was and how you would establish coordinates for it.

But that's the problem, you can't look at the propagation of a light beam. How would you do that? It's not like watching a bullet traveling at a high speed and which you shine light on so you can see where it is at any particular time. What do you use to watch the propagation of the light beam? I'm assuming of course that the beam has been just turned on and what you are talking about is the leading edge of the beam. Think about it.

I see the problem with the way I asked it, so let me rephrase the question. Let's do a round trip light beam test in a moving IRF and measure round trip time from point A to point B (mirror) back to point A. There are two observers, Stationary Sam at rest (with respect to the aether) watching this test moving by, and Moving Moe co-moving with the test instruments, mirror, etc. Moving Moe makes his light speed calculations as though he's stationary.

Would 1904 Lorentz have had any trouble figuring out what speed Moving Moe would come up with for the light when making his measurements in the moving IRF? Would he have any trouble with Stationary Sam's interpretation of the test results reported by Moe?

This is the essence of the issue between scientists prior to Einstein and Einstein. They just assumed that light propagated at c only in the rest state of the ether that pervaded the universe.

So far so good. But did this mean that they did not understand relativistic velocity addition? Or should I take it to mean that they could have worked it out, but hadn't yet done so, or that they had done so, but hadn't yet understood the implications of the math - that each moving observer measures light speed to be c? Or ... see below

Einstein said that everything would work just fine if you made that exact same assumption in any inertial frame. But either way, there is no way to prove or measure or conclude in any absolute sense which assumption is correct. Einstein simply used the assumption as the basis for establishing what a frame was and how you would establish coordinates for it.

If I understand this, you're saying that using Lorentz transforms of 1904 vintage they would reach the exact same conclusions for all physical measurements as reached by SR. They merely placed a different interpretation on things - as though there is a "preferred" IRF in which the unmeasurable, intangible, aether is stationary and all other frames move relative to it and have to have measurements made within them transformed by Lorentz equations.

I regret if I'm being slow, but would it be correct to say that Lorentz thought Moving Moe's experimental results were somehow less valid than Stationary Sam's (if SS did the same experiments as MM) while Einstein thought they were equally valid?

I see the problem with the way I asked it, so let me rephrase the question. Let's do a round trip light beam test in a moving IRF and measure round trip time from point A to point B (mirror) back to point A. There are two observers, Stationary Sam at rest (with respect to the aether) watching this test moving by, and Moving Moe co-moving with the test instruments, mirror, etc. Moving Moe makes his light speed calculations as though he's stationary.

Would 1904 Lorentz have had any trouble figuring out what speed Moving Moe would come up with for the light when making his measurements in the moving IRF? Would he have any trouble with Stationary Sam's interpretation of the test results reported by Moe?

Shortly after the famous Michelson-Morley experiment failed to detect any ether wind, Lorentz had explained it with Length Contraction. The scientists of the time were well aware that they were measuring the two-way speed of light and that it always came out the same but with Length Contraction and Time Dilation, they realized that they could not determine the rest state of the ether. Everybody assumed that we were all Moving Moe's and not Stationary Sam's. If it had turned out that the two-way measurement of the speed of light were different in different directions, then they could have figured out how light propagated but since it comes out the same, they can't determine the one-way speed of light. They understood this but they continued to believe that it was c only in the rest state of the ether.

So far so good. But did this mean that they did not understand relativistic velocity addition? Or should I take it to mean that they could have worked it out, but hadn't yet done so, or that they had done so, but hadn't yet understood the implications of the math - that each moving observer measures light speed to be c? Or ... see below

If I understand this, you're saying that using Lorentz transforms of 1904 vintage they would reach the exact same conclusions for all physical measurements as reached by SR. They merely placed a different interpretation on things - as though there is a "preferred" IRF in which the unmeasurable, intangible, aether is stationary and all other frames move relative to it and have to have measurements made within them transformed by Lorentz equations.

I regret if I'm being slow, but would it be correct to say that Lorentz thought Moving Moe's experimental results were somehow less valid than Stationary Sam's (if SS did the same experiments as MM) while Einstein thought they were equally valid?

So would the 1904 Lorentz have understood that two different observers, in two different IRFs moving at a constant speed relative to each other and looking at the same propagating light beam would each independently conclude that the light they were examining (with their co-moving instruments in their independent IRFs) was traveling at speed c relative to his IRF? Don't the LET equations force that?

I don't think that he would have put it like that, for he used a different definition of "speed of light"; and apart of that, in 1904 he didn't even fully understood the physical meaning of his equations. Still, what you ask reminds me of his "corresponding states" and you may find the following commentary interesting:http://www.mathpages.com/rr/s1-05/1-05.htm

Would 1904 Lorentz have had any trouble figuring out what speed Moving Moe would come up with for the light when making his measurements in the moving IRF? Would he have any trouble with Stationary Sam's interpretation of the test results reported by Moe?

He had found the correct transformation equations from which these things directly follow, so it should not have given him trouble.

Thanks to all for the helpful guidance. I started with the impression that Lorentz had the answers before Einstein, while Einstein had the deeper meaning of those answers before Lorentz. I suppose I finish with the same impression, but at least it's confirmed and I have a deeper appreciation of the historical context of SR.